Communication apparatus and communication method using digital wavelet multi carrier transmission system

ABSTRACT

In case of disposing a pilot symbol in data transmission which depends on a DWMC transmission system, in a plurality of transmission symbols on a time axis, a pilot symbol, which becomes a signal of a sine wave, is configured, by giving contiguous identical data in a plurality of predetermined symbols. By transmitting a transmission signal with the use of this pilot signal, between a transmitting device and a receiving device, it is possible to carry out channel equalization by complex information which is obtained from a pilot symbol.

BACKGROUND OF THE INVENTION

The present invention relates to a communication apparatus and acommunication method of a multi carrier transmission system, and inparticular, to a communication apparatus and a communication methodusing a multi carrier transmission method (Digital Wavelet MultiCarrier-transmission system, hereinafter, described as “DWMCtransmission system”) which carries out data transmission by digitalmodulating and demodulating processing with the use of a realcoefficient wavelet filter bank.

In a terrestrial digital broadcasting system etc., wide band datatransmission is enabled by a multi carrier transmission system with theuse of OFDM (Orthogonal Frequency Division Multiplexing). As a datatransmission system depending on this type of the multi carriertransmission system with the use of OFDM, a multi carrier transmissionmethod depending on digital modem processing with the use of a realcoefficient wavelet filter bank (DWMC transmission method) has beenproposed. In the DWMC transmission method, a plurality of digitalmodulated waves are combined by use of the real coefficient filter bank,and thereby, transmission signals are generated. As a modulation systemof each carrier, PAM (Pulse Amplitude Modulation) etc. are used.

Data transmission, which depends on the DWMC transmission method, willbe described by use of FIGS. 15 to 18. FIG. 15 is a view which shows anexample of an wavelet wave form, and FIG. 16 is a view which shows anexample of a transmission wave form in the DWMC transmission method, andFIG. 17 is a view which shows an example of a transmission spectrum inthe DWMC transmission method, and FIG. 18 is a view which shows aconfiguration example of a transmission frame in the DWMC transmissionmethod.

In the data transmission which depends on the DWMC transmission method,as shown in FIG. 15, impulse responses of each sub carrier aretransmitted over being overlapped in each sub carrier. Each transmissionsymbol becomes such a time wave form that impulse responses of each subcarrier were combined, as shown in FIG. 16. An example of an amplitudespectrum is shown in FIG. 17. In the DWMC transmission method,approximately several dozen through several hundred of transmissionsymbols in FIG. 16 are collected to configure one transmission frame. Aconfiguration frame of the DWMC transmission frame is shown in FIG. 18.In this DWMC transmission frame, a symbol for frame synchronization, asymbol for equalization etc. are included in addition to a symbol forinformation data transmission.

FIG. 19 is a block diagram which shows a conceptual configuration of acommunication apparatus as a past example, which is configured by havinga transmitting device and a receiving device in case that the DWMCtransmission system was adopted.

In FIG. 19, a receiving device 199 is configured by having an A/Dconverter 110 which carries out analog-digital conversion, a wavelettransform unit 120 which carries out discrete wavelet transformation, aparallel/serial (P/S) converter 130 which converts parallel data intoserial data, and a decision unit 140 which carries out judgment ofreceived signals. A transmitting device 299 is configured by having asymbol mapper 210 which converts bit data into symbol data to carry outsymbol mapping, a serial/parallel (S/P) converter 220 which convertsserial data into parallel data, an inverse wavelet transform unit 230which carries out inverse discrete wavelet transformation, and a D/Aconverter 240 which carries out digital-analog conversion.

An operation of the communication apparatus with the above-describedconfiguration will be described. Firstly, in the transmitting device299, bit data of transmission data is converted into symbol data by thesymbol mapper 210, and symbol mapping (PAM) is carried out in accordancewith each symbol data. Then, serial data is converted into parallel databy the S/P converter 220, and thereby, a real number value di (i=1˜M, Mis a plural number) is given to symbol data with respect to each subcarrier. After that, this real number value is inverse discrete wavelettransformed on a time axis by the inverse wavelet transform unit 230. Bythis means, sample values of time axis wave forms are generated, and asample value series, which represents transmission symbols, isgenerated. Then, this sample value series is converted into analog baseband signal wave forms which are continuing in terms of time by the D/Aconverter 240, and then, transmitted. Here, the number of sample valueson a times axis, which are generated by the inverse discrete wavelettransformation, is normally 2 to the n-th power pieces (n is a positiveinteger).

In the receiving device 199, analog base band signal wave forms, whichare obtained from received signals, are sampled with the same samplerate as that of a transmitting side by the A/D converter 110, to obtaina sample value series. Then, this sample value series is discretewavelet transformed on a frequency axis by the wavelet transform unit120, and parallel data is converted into serial data by the P/Sconverter 130. Finally, an amplitude value of each sub carrier iscalculated in the decision unit 140, and judgment of a received signalis carried out to obtain reception data.

In addition, as an example of the communication apparatus with the useof the DWMC transmission method, proposed is a power line carriercommunication apparatus which carries out data transmission by utilizinga power line which were disposed in a house etc., as communicationmedium (e.g., see, JP-A-2003-218831).

In the meantime, in the multi carrier transmission system, there is acase to dispose a pilot symbol for transmitting a pilot signal by use ofa sine wave signal in a predetermined symbol, in order to carry outadjustment etc. of a phase of transmission data. By information of thispilot symbol, it becomes possible to adjust an amplitude and a phase oftransmission data, and to improve an equalization characteristic of achannel characteristic (compensation of a transmission characteristic,etc.) between a transmitting device and a receiving device.

A past multi carrier transmission system with the use of FFT (FastFourier Transform) based OFDM is one which carries out FFT as complexnumber conversion, and therefore, it is possible to generate a pilotsymbol having complex information which represents an amplitude and aphase, only by transmitting a known signal (e.g., a signal in whichidentical data such as all 1 continues) by use of one symbol, in case ofdisposing a pilot symbol (e.g., see, JP-A-2000-278237).

In contrast to this, a multi carrier transmission system, which dependson wavelet transformation based OFDM to be used in the DWMC transmissionmethod, is one which carried out wavelet transformation as real numberconversion, and in addition, even if a pilot symbol, which was simplyconfigured by one symbol, is demodulated, it is not possible to obtaincomplex information since a filter length is longer than a symbollength, and therefore, in the multi carrier transmission system whichdepends on wavelet transformation based OFDM, a pilot symbol was notused.

SUMMARY OF THE INVENTION

The invention is one which was made in view of the above-described pastcircumstances, and aims to provide a multi carrier transmission systemcommunication apparatus and communication method, in which it ispossible to use a pilot symbol which can handle complex information, indata transmission of a multi carrier transmission system which dependson wavelet transformation based OFDM for carrying out real coefficientwavelet transformation.

According to the present invention, a communication apparatus of a multicarrier transmission system, which carries out data transmission bydigital modem processing, comprises: a modulator which inserts at leastone symbol to which contiguous identical data was given into atransmission signal as a pilot symbol, and carries out digital multicarrier modulation processing of transmission signals by use of a filterbank subjecting wavelet transformation; and a transmitter fortransmitting transmission signals including said pilot symbol, which hasbeen subjected the digital multi carrier modulation processing by saidmodulator.

A communication apparatus of a multi carrier transmission system, whichcarries out data transmission by digital modem processing, comprising: areceiver for receiving transmission signals including a pilot symbolconfigured by at least one symbol to which contiguous identical data wasgiven; and a demodulator which carries out digital multi carrierdemodulation processing of transmission signals received by saidreceiver with use of a filter bank subjecting wavelet transformation.

Thus, it is possible to provide a communication apparatus and acommunication method of a multi carrier transmission system, which iscapable of using a pilot symbol which can handle complex information, indata transmission of a multi carrier transmission system which dependson wavelet transformation based OFDM for carrying out real coefficientwavelet transformation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are block diagrams which show a major configuration of acommunication apparatus which relates to a first embodiment of theinvention;

FIGS. 2A and 2B are views which show one example of a schematicconfiguration of an inverse wavelet transform unit and a filter bankcircuit which a wavelet transform unit has in the first embodiment;

FIG. 3 is a view which schematically shows a part of a transmissionframe on a time axis in the first embodiment;

FIG. 4 is a block diagram which shows a major configuration of areceiving device in a second embodiment of the invention;

FIG. 5 is a view which schematically shows a part of a transmissionframe on a time axis in the second embodiment;

FIG. 6 is a view which schematically shows a part of a transmissionframe on a time axis in a third embodiment of the invention;

FIG. 7 is a view which shows a calculation example of complexinformation on an orthogonal plane in the third embodiment;

FIG. 8 is a view which schematically shows a part of a transmissionframe on a time axis in a fourth embodiment of the invention;

FIGS. 9A and 9B are views which show a calculation example of complexinformation on an orthogonal plane in the fourth embodiment;

FIG. 10 is a view which schematically shows a part of a transmissionframe on a time axis in a fifth embodiment of the invention;

FIG. 11 is a view which shows a calculation example of complexinformation on an orthogonal plane in the fifth embodiment;

FIGS. 12A and 12B are views which schematically shows a part of atransmission frame on a time axis in a seventh embodiment of theinvention;

FIGS. 13A and 13B are block diagrams which show a major configuration ofa communication apparatus which relates to an eighth embodiment of theinvention;

FIG. 14 is a view which schematically shows a part of a transmissionframe on a time axis in the eighth embodiment;

FIG. 15 is a view which shows an example of a wavelet wave form;

FIG. 16 is a view which shows an example of a transmission wave form ina DWMC transmission method;

FIG. 17 is a view which shows an example of a transmission spectrum inthe DWMC transmission method;

FIG. 18 is a view which shows a configuration example of a transmissionframe in the DWMC transmission method;

FIG. 19 is a block diagram which shows a conceptual configuration of acommunication apparatus as a past example, which has a transmittingdevice and a receiving device in case that the DWMC transmission methodwas adopted;

FIG. 20 is an external appearance perspective view which shows acommunication apparatus (front surface);

FIG. 21 is an external appearance perspective view which shows thecommunication apparatus (rear surface); and

FIGS. 22A and 22B are block diagrams which show a modified example of aconfiguration of a communication apparatus which uses a power line as achannel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this embodiment, a configuration and an operation of a communicationapparatus, which carries out data transmission by use of a multi carriertransmission method (DWMC transmission method) which depends on digitalmodem processing with the use of a real coefficient wavelet filter bank.

First Embodiment

FIG. 20 is an external appearance perspective view which shows acommunication apparatus (front surface), and FIG. 21 is an externalappearance perspective view which shows the communication apparatus(rear surface). A communication apparatus 100 in this embodiment is amodem as shown in FIGS. 20 and 21. This communication apparatus 100 isone which configures a transmitting device 70 or a receiving device 80which will be described later.

The communication apparatus 100 has a housing 101. On a front surface ofthe housing 101, a display section 106 such as LED (Light EmittingDevice) is disposed as shown in FIG. 20. On a rear surface of thehousing 101, a power connector 102, a LAN (Local Area Network) modularjack 103 such as RJ45, and a Dsub connector 104 are disposed as shown inFIG. 21. To the power connector 102, a power line 107 such as a parallelcable is connected as shown in FIG. 21. To the modular jack 103, a LANcable, which is not shown in the figure, is connected. To the Dsubconnector 104, a Dsub cable, which is not shown in the figure, isconnected.

To the power line 107, a commercial power source such as alternatingvoltage is applied, and when a pilot symbol, which will be describedlater, is outputted, the pilot symbol is overlapped with the alternatingvoltage through a coupler transformer which is not shown in the figure.Meanwhile, as one example of the communication apparatus, the modem inFIGS. 20 and 21 was shown, but there is no particular need to limit tothis, and the communication apparatus may be an electric equipment whichwas equipped with a modem (e.g., a household electrical appliance suchas a television receiver).

FIGS. 1A and 1B are block diagrams which show a major configuration of acommunication apparatus which relates to a first embodiment of theinvention. FIG. 1A is a block diagram showing a transmitting devicewhich configures the communication apparatus, and FIG. 1B is a blockdiagram showing a receiving device which configures the communicationapparatus.

A transmitting device 10 is configured by having a transmission dataoutput section 11 which outputs transmission data, a pilot data outputsection 12 which outputs pilot data for a pilot signal, a switch 13which carries out a switching selection of transmission data or pilotdata, a symbol mapper 14 which converts bit data into symbol data tocarry out symbol mapping, an inverse wavelet transform unit 15 whichcarries out inverse discrete wavelet transformation, and a D/A converter16 which carries out digital-analog conversion. In the transmittingdevice 10, the D/A converter 16 has a function of transmitter.

Meanwhile, the transmission data output section 11, the pilot dataoutput section 12, the switch 13, the symbol mapper 14, and the inversewavelet transformer 15 are configured by a MAC/PHY-IC chip (not shown inthe figure) which carries out management of a MAC (Media Access Control)level and a PHY (Physical) layer. The D/A converter 16 is configured byan AFE (Analog Front End) IC chip (not shown in the figure).

A receiving device 20 is configured by having an A/D converter 21 whichcarries out analog-digital conversion, a wavelet transform unit 22 whichcarries out discrete wavelet transformation, a pilot symbol extractionsection 23 which extracts a pilot symbol from received signals, achannel frequency characteristic estimation section 24, and a channelequalizer 25 which carries out equalization of a transmissioncharacteristic (compensation of a transmission characteristic, etc.)between the transmitting device 10 and the receiving device 20. In thereceiving device 20, the A/D converter 21 has a function of receiver.

Meanwhile, the wavelet transformer 22, the pilot symbol extractionsection 23, the channel frequency characteristic estimator 24, and thechannel equalizer 25 are configured by a MAC/PHY-IC chip (not shown inthe figure) which carries out management of a MAC (Media Access Control)level and a PHY (Physical) layer. The A/D converter 21 is configured byan AFE (Analog Front End) IC chip (not shown in the figure).

In the transmitting device 10, in case of outputting transmission data,the transmission data output section 11 is connected to the symbolmatter 14 by switching selection of the switch 13. At this time, bitdata of arbitrary transmission data, which is outputted from thetransmission data output section 11, is converted into symbol data bythe symbol mapper 14, and symbol mapping (PAM) is carried out inaccordance with each symbol data. After that, by the inverse wavelettransform unit 15, serial data is converted into parallel data and areal number value di (i=1˜M, M is a plural number) is given to thesymbol data with respect to each sub carrier, and thereafter, data ofthis real number value is inverse discrete wavelet transformed on a timeaxis. A filter bank subjecting a wavelet transformation using a rearcoefficient will be referred as a real coefficient wavelet filter bank,hereinafter. By this means, sample values with time axis wave forms aregenerated, and a sample value series, which represents transmissionsymbols, is generated. Then, by the D/A converter 16, this sample valueseries is converted into analog base band signal wave forms which arecontinuing in terms of time, and then, transmitted.

In addition, in case of outputting a pilot symbol, the pilot data outputsection 12 is connected to the symbol mapper 14 by switching selectionof the switch 13. At this time, bit data of pilot data, which isoutputted from the pilot data output section 12, is converted intoserial data by the symbol mapper 14. Then, by the inverse wavelettransform unit 15, serial data is converted into parallel data, andthereby, contiguous identical data (e.g., all 1, all 0, etc.) is givento a relevant symbol, and this data is inverse discrete wavelettransformed on a time axis. After that, by the D/A converter 16, it isconverted into an analog base band signal wave form which includes apilot symbol, and then, transmitted. The contiguous identical data is adata series which corresponds to each symbol and is configured byconsecutive identical values (e.g., 0 or 1), and for example, contiguousidentical data, which corresponds to 1 symbol, is configured by all 1(1, 1, 1, . . . , 1), and contiguous identical data, which correspondsto 2 symbol, is configured by all 0 (0, 0, 0, . . . 0), and contiguousidentical data, which corresponds to K symbol, is configured by all 1(1, 1, 1, . . . , 1).

In the above-described transmitting device 10, the inverse wavelettransform unit 15 is one which has a function of demodulator, and thepilot data output section 12 and the switch 13 are ones having afunction of pilot symbol generator.

In the receiving device 20, analog base band signal wave forms, whichare obtained from received signals by the A/D converter 21, are sampledwith the same sampling rate as that of a transmitting side, and a samplevalue series is obtained. Then, by the wavelet transform unit 22, thissample value series is discrete wavelet transformed on a frequency axis,and parallel data is converted into serial data. The, by the pilotsymbol extraction section 23, a pilot symbol is extracted from receivedsignals, and by the channel frequency characteristic estimation section24, a frequency characteristic of a channel is estimated. Then, anequalization amount for carrying out compensation etc. of a transmissioncharacteristic of a channel by the channel equalizer 25, through the useof this channel estimation information, with respect to each subcarrier, is obtained and equalization of received signals is carriedout.

In the above-described receiving device 20, the wavelet transform unit22 is one which has a function of demodulator, and the pilot symbolextraction section 23 is one which has a function of pilot symbolextractor, and the channel frequency characteristic estimation sectionis one which has a function of channel characteristic estimation means.

FIGS. 2A and 2B are views which show one example of a schematicconfiguration of a filter bank circuit which the inverse wavelettransform unit and the wavelet transform unit of the first embodimenthave. Particularly, FIG. 2A shows a band combining filter bank circuit,and FIG. 2B shows a band division filter bank circuit, respectively.Meanwhile, in this embodiment, as one example of a filter bank circuit,a configuration of a filter bank circuit, which was configured by acommonly used FIR filter, will be described.

As shown in FIG. 2A, the synthesis filter bank circuit 30 is configuredby having an up sampler 31 which realizes N times multiple of a samplingrate of signals, a FIR filter group 33 in which a plurality of FIR(Finite Impulse Response) filters 32, which are orthogonal with eachother, were combined, and a two input adder 34. The inverse wavelettransform unit 15 is configured by having this synthesis filter bankcircuit 30.

In addition, as shown in FIG. 2B, the analysis filter bank circuit 35has a FIR filter group 37 in which a plurality of FIR filters 36, whichare orthogonal with each other, were combined, and a down sampler 38which realizes 1/N times of a sampling rate. A wavelet transform unit 22is configured by having this analysis filter bank circuit 35.

Here, assuming that the number of taps in the FIR filter 32 is N, eachFIR filter 32 is equipped with (N−1) pieces of delay elements fordelaying input data, N pieces of multipliers for multiplying acoefficient to output data and the above-described input data of thisdelay element, (N−1) pieces of adders for obtaining an accumulated valueby adding output data of this multiplier from an input sidesequentially. Meanwhile, assuming that the number of sub carriers to bedivided is M (M is 2 to the power), the tap number N of the FIR filter32 is represented by a real number multiple (K times) of M.

Next, generation of a pilot symbol according to this embodiment will bedescribed. FIG. 3 is a view which schematically shows a part of atransmission frame on a time axis in the first embodiment. FIG. 3 showsa part of an information symbol in a transmission frame shown in FIG.18.

As shown in FIG. 3, in case that a filter length of wavelet (a filterlength of the FIR filter 36 in FIG. 2) is composed of K symbols, a pilotsymbol P is composed of contiguous identical data (e.g., all 1, all 0,etc.) for 2K−1 symbols at a transmitting side. Meanwhile, in FIG. 3 andexplanation of the embodiment of the invention, it will be described,taking a case of a wavelet's filter length K=4 symbols, as an example.

Here, in case of a past multi carrier transmission system which dependson FFT based OFDM, a wavelength of one symbol length is obtained inaccordance with a data signal of one symbol. Therefore, a sine wavesignal is obtained by a pilot symbol which was configured by contiguousidentical data for one symbol, and therefore, it is possible toconfigure a pilot symbol by one symbol.

On one hand, in case of wavelet based OFDM, as described in FIG. 2, datais transmitted by use of a filter bank which includes a filter having apredetermined filter length. On that account, as shown in FIG. 3,wavelet wave forms with a length of K symbols are transmitted to a datasignal of one symbol, with a shift of one symbol length at a time.

For example, as shown in FIG. 3, a wavelet wave form WD1 of data whichwas given to a symbol D1 is transmitted with wave forms for 4 symbols.Then, a receiving side can demodulate a data signal D1, by receivingthis wave form WD1 for 4 symbols.

Here, it is not possible to obtain a sine wave by simply inserting onlycontiguous identical data P1, due to influence of a wavelet wave form ofdata which was given to previous and next symbols, and therefore, it isnot possible to use information of a point of a signal which wasdemodulated at a receiving side, as a pilot signal, withoutmodification.

Consequently, in this embodiment, a pilot symbol is composed ofcontiguous identical data of 2K−1 symbols, and the pilot symbol isinserted into the transmission frame (transmission signal). The symbolsP4 through P7 which show sine waves, i.e., later K symbols among themare subjected wavelet transformation, then, its signal point is used asa pilot symbol.

Firstly, in a 4-th symbol (K-th symbol) of contiguous identical data P1through P4, it becomes difficult to have an influence of a wavelet waveform WD2 which depends on transmission data, and only contiguousidentical data enters into a wavelet filter, and therefore, a time waveform becomes a sine wave. Then, a wavelet wave form WP4 of contiguousidentical data of that P4 has further a length of 4 symbols (K symbols),and therefore, it is configured so as for a time wave form to show aside wave in the symbols P4 through P7, by giving contiguous identicaldata to the symbols P4 through P7 for 4 symbols' filter lengthsincluding the 4-th symbol P4. Then, by wavelet converting these symbolsP4 through P7 which have become sine waves, it is possible to use themas a pilot symbol.

Then, on the basis of this extracted pilot symbol, equalization of achannel is carried out by a channel equalizer in such a manner that atransmission frequency characteristic such as a phase and frequency isestimated, and a demodulated signal is controlled by use of its inversecharacteristic, and so on.

In this manner, according to the first embodiment, a pilot symbol, whichcan handle complex information for channel equalization, can beconfigured by a pilot symbol which was generated by giving contiguousidentical data across continuing 2K−1 symbols, and can be used. Inaddition, by carrying out equalization of a channel through the use ofinformation of a pilot symbol, it is possible to follow channelcharacteristic fluctuation.

Meanwhile, this embodiment described such a case that a pilot symbol iscomposed of 2K−1 symbols to which contiguous identical data was given,but it is all right if they are 2K−1 symbols or more. In addition, inthe receiving device, if a K-th symbol or later is demodulated in apilot symbol of 2K−1 symbols or more, it is possible to obtain complexinformation.

FIGS. 22A and 22B are block diagrams which show a modified example of aconfiguration of a communication apparatus which uses a power line as achannel. Particularly, FIG. 22A shows a transmitting device, and FIG.22B shows a receiving device. In the transmitting device and thereceiving device shown in FIGS. 22A and 22B, identical referencenumerals and signs are applied to identical elements to those of thetransmitting device and the receiving device shown in FIGS. 1A and 1B,and thereby, explanations thereof will be omitted. A transmitting device70 of FIG. 22A has BPF (Band Pass Filter) 17 and a coupler transformer18, in addition to each element of the transmitting device of FIG. 1A.The coupler transformer 18 is connected to the power line 107. Inaddition, a receiving device 80 of FIG. 22B has BPF 26 and a couplertransformer 27, in addition to each element of the receiving device ofFIG. 1B. The coupler transformer 27 is connected to the power line 107.

The transmission data output section 11, the pilot data output section12, the switch 13, the symbol mapper 14, and the inverse wavelettransformer 15 are configured by a MAC/PHY-IC chip (not shown in thefigure) which carries out management of a MAC (Media Access Control)level and a PHY (Physical) layer. The D/A converter 16 and BPF 17 areconfigured by an AFE (Analog Front End) IC chip (not shown in thefigure).

In the transmitting device 70, when the D/A converter 16 outputs analogbase band signal wave forms, BPF 17 gets through transmission wave formsin a predetermined frequency band. The coupler transformer 18 overlapsthe transmission wave forms from BPF 17 with the alternating voltage,and transmits them through the power line 107. On one hand, in thereceiving device 80, when signals, which were transmitted through thepower line 107, have been received, the coupler transformer 27 separatesthe received signals from the alternating voltage, and BPF 26 getsthrough received signals in a predetermined frequency band. The A/Dconverter 21 samples analog base band signal wave forms which areobtained from the received signals, and will hereinafter carry out thesame processing as that of the receiving device of FIG. 1B.

The wavelet transformer 22, the pilot symbol extraction section 23, thechannel frequency characteristic estimator 24, and the channel equalizer25 are configured by a MAC/PHY-IC chip (not shown in the figure) whichcarries out management of a MAC (Media Access Control) level and a PHY(Physical) layer. The A/D converter 21 and BPF 26 are configured by anAFE (Analog Front End) IC chip (not shown in the figure).

Meanwhile, in the transmitting device 70, the D/A converter 16, BPF 17,and the coupler transformer 18 are one which has a function of atransmission section. In the receiving device 80, the couplertransformer 27, BPF 26, and the A/D converter 21 are one which has afunction of a receiving section.

Second Embodiment

FIG. 4 is a block diagram which shows a major configuration of areceiving device which relates to a second embodiment of the invention.Meanwhile, identical reference numerals and signs are given to similarconstituent elements to those in the first embodiment 1.

A receiving device 40 in the second embodiment is configured by having aFourier transform unit 41 which carries out Fourier transformation to asymbol extracted by a pilot symbol extraction section 23, together withan A/D converter 21, a wavelet transform unit 22, the pilot symbolextraction section 23, a channel frequency characteristic estimationsection 24, and a channel equalizer 25. Meanwhile, in the receivingdevice 40, the Fourier transform unit 41 is one which has a function ofFourier transformer.

Next, generation of a pilot symbol according to this embodiment will bedescribed. FIG. 5 is a view which schematically shows a part of atransmission frame on a time axis in the second embodiment. In thisembodiment, in case of disposing a pilot symbol in data transmission byuse of the DWMC transmission system and in case that a filter length ofwavelet is composed of K symbols, contiguous identical data (e.g., all1, all 0, etc.) for K symbols is given in a transmitting side, and aK-th symbol, among that continuing K symbols, is Fourier transformed ina receiving side, and thereby, it becomes possible to directly handledemodulated signal points as polar coordinates. Meanwhile, as shown inFIG. 5, in this embodiment, a case of a filter length K=4 will bedescribed as example.

As shown in FIG. 3, an influence of a wave form due to transmission dataprior to pilot data is applied up to a 3-rd symbol ((K−1)-th symbol),but an influence of a wave form due to transmission data prior to pilotdata is not applied to pilot data P4 of a 4-th symbol (K-th symbol), andtherefore, a sine wave signal is obtained.

However, in case of obtaining a demodulated signal by carrying outwavelet transformation, in order to obtain a sine wave signal for afilter length, contiguous identical data of 3 symbols (K−1 symbols) isfurther required, but in this embodiment, only one symbol of the symbolP4, which becomes a sine wave as a time wave form, is Fouriertransformed, and thereby, complex is obtained from that demodulatedsignal point information. On the basis of that complex information,estimation of a channel characteristic is carried out by the channelfrequency characteristic estimation section 24, and channel equalizationis carried out by the channel equalizer 25.

In this manner, according to the second embodiment, it is possible toconfigure a pilot symbol as described above, and to configure a pilotsymbol with the same symbol number as a filter length of wavelet.

Third Embodiment

FIG. 6 is a view which schematically shows a part of a transmissionframe on a time axis in a third embodiment of the invention. A majorconfiguration of a communication apparatus of this embodiment is almostthe same as that of the first embodiment which was described in FIG. 1.

As shown in FIG. 6, in the third embodiment, a transmitting deviceconfigures a pilot symbol P by use of contiguous identical data P1 forone symbol, and transmits it to a receiving device.

However, in this case, even if the pilot symbol P is composed of onesymbol of only the contiguous identical data P1, a sine wave is notobtained, and therefore, complex information is not obtained from itsdemodulated signal point information without modification. Consequently,in the third embodiment, in a channel frequency characteristicestimation section 20, complex information is calculated on the basis ofdemodulated signal point information between adjacent sub carriers.Meanwhile, the channel frequency characteristic estimation section 20 inthis embodiment has a function of complex information estimator.

FIG. 7 is a view which shows a calculation example of complexinformation on an orthogonal plane in the third embodiment. As shown inFIG. 7, it is assumed that a demodulation signal point in a sub carrierm is R_(m), and a demodulated signal point in a sub carrier m+1 which isadjacent to the sub carrier m is R_(m+1). Then, a straight line L1,which runs through the point R_(m) and the point R_(m+1), is made. Then,as to an intersection point P of a perpendicular line, which was madefrom an original point O to the straight line L1, and the straight lineL1, obtained is complex information in which a distance A between thepoint P and the original point P was used as an amplitude, and an angleθ, which is made by an I axis and a line segment OP, was used as aphase. Then, the channel frequency characteristic estimation section 24estimates a frequency characteristic of a channel on the basis of thiscomplex information, and the channel equalizer 25 carries outequalization of the channel on the basis of that channel characteristic.

Meanwhile, a straight line L0 shows an area in which a demodulatedsignal point exists in case that synchronization was carried outaccurately. In the example shown in FIG. 7, the straight line L1 isdeviated from the straight line L0. This represents that an amplitudeand a phase are fluctuating by an actual channel characteristic.

In this manner, according to the third embodiment, it is possible toconfigure a pilot symbol, which can handle complex information forchannel equalization, with the use of at leas one symbol, by calculatingcomplex information from demodulation signal point information ofadjacent sub carriers.

Fourth Embodiment

FIG. 8 is a view which schematically shows a part of a transmissionframe on a time axis in a fourth embodiment of the invention. A majorconfiguration of a communication apparatus in this embodiment is almostthe same as that of the first embodiment which was described in FIG. 1.In addition, In FIG. 8, as one example of the filter length K ofwavelet, a case of 4 symbols will be described.

As shown in FIG. 8, in the fourth embodiment, a transmitting deviceconfigures a pilot symbol P by use of contiguous identical data P1through P3 for 3 symbols (K−1 symbols), and transmits it to a receivingdevice. Then, the receiving device obtains complex information by use ofsuch a demodulated signal point that K−1 symbol P3 of the pilot symbolwas wavelet transformed.

However, since the contiguous identical data P1 through P3 are less than4 symbols as a filter length, even if the pilot symbol P is composed of3 symbols of P1 through P3, a sine wave is not obtained, and it is notpossible to use it as a channel characteristic as it is, from thatdemodulated signal point information.

Consequently, in the fourth embodiment, in the same manner as the thirdembodiment, in the channel frequency characteristic estimation section20, complex information is calculated on the basis of demodulated signalpoint information between adjacent sub carriers. Further, in thisembodiment, a pilot symbol is configured by use of contiguous identicaldata for K−1 symbols.

FIGS. 9A and 9B are view which shows a calculation example of complexinformation on an orthogonal plane in the fourth embodiment.Particularly, FIG. 9A is a view which shows such a case that a 3-rdsymbol P3 ((K−1)-th symbol) of a pilot symbol, which is configured by 3symbols (K−1), was wavelet transformed, and FIG. 9B shows such a casethat ones other than the 3-rd symbol ((K−1)-th symbol) were wavelettransformed.

Here, the more the number of symbols of contiguous identical data, whichconfigures a pilot symbol, comes close to the filter length K symbols,the more a wave length to be obtained comes close to a sine wave. Here,signal points of adjacent sub channels, in case that a sine wave wasdemodulated, become +1 and −1, respectively. Therefore, in case thatsymbols of contiguous identical data are given continuously, a latersymbol comes close to a sine wave, and therefore, a distance betweensignal points of adjacent sub channels is broden.

At this time, as shown in FIGS. 9A and 9B, the wider a distance betweentwo signal point information R_(m) and R_(m+1) is, the fewer a devianceof the straight line L1 due to an error of a demodulated signal pointbecomes. For example, a straight line L2 is one showing such a case thatthere is no error of signal points, and in FIG. 9A, since two signalpoints are displaced, there is few deviance of the straight lines L1 andL2 due to an error of a signal point, but in FIG. 9B, since two signalpoints are close, deviance of the straight line L1 and the straight lineL2 is enlarged due to an error of a signal point. Therefore, byconfiguring a pilot symbol in such a manner that two demodulated signalpoints have a fixed distance or more, it is possible to reduce an errorof a point P for obtaining complex information, and therefore, it ispossible to improve accuracy of channel characteristic estimation.

In this manner, according to the fourth embodiment, it is possible tocarry out channel characteristic estimation with high accuracy, even incase that a pilot symbol, which can handle complex information forchannel equalization, was configured by the number of symbols which isless than the filter length K symbols, by calculating complexinformation from demodulated signal point information of adjacent subcarriers.

Fifth Embodiment

FIG. 10 is a view which schematically shows a part of a transmissionframe on a time axis in a fifth embodiment of the invention. A majorconfiguration of a communication apparatus of this embodiment is almostthe same as that of the first embodiment which was described in FIG. 1.

As shown in FIG. 10, in the fifth embodiment, a transmitting deviceconfigures a pilot symbols P by contiguous identical data P1, P2 for 2symbols, and transmits it to a receiving device.

However, in this case, even if the pilot symbol P is configured by 2symbols of only contiguous identical data P1, P2, it is less than 4(K)symbols of a filter length, and therefore, even if the pilot symbol P isconfigured by 3 symbols of P1 through P3, a sine wave is not obtained,and it is not possible to use it from its demodulated signal pointinformation as it is, as a channel characteristic. Consequently, in thefifth embodiment, in a channel frequency characteristic estimationsection 20, as to ones that the contiguous identical data P1, P2 werewavelet transformed respectively, complex information is calculated onthe basis of demodulated signal point information of an identical subcarrier.

FIG. 11 is a view which shows a calculation example of complexinformation on an orthogonal plane in the fifth embodiment. As shown inFIG. 11, it is assumed that a demodulated signal point of a first symbolP1 in a sub carrier m is R1, and a demodulated signal point of a secondsymbol P2 in the sub carrier m is R2. Then, a straight line L1, whichruns through the point R1 and the point R2, is made. Then, as to anintersection point P of a perpendicular line, which was made from anoriginal point O to the straight line L1, and the straight line L1,obtained is complex information in which a distance A between the pointP and the original point P was used as an amplitude, and an angle θ,which is made by an I axis and a line segment OP, was used as a phase.Then, the channel frequency characteristic estimation section 24estimates a frequency characteristic of a channel on the basis of thiscomplex information, and updates equalization information of a channelequalizer 25.

Meanwhile, a straight line L0 shows an area in which a demodulatedsignal point exists in case that synchronization was carried outaccurately. In the example shown in FIG. 11, the straight line L1 isdeviated from the straight line L0. This represents that an amplitudeand a phase are fluctuating by an actual channel characteristic.

In this manner, according to the fifth embodiment, it is possible toconfigure a pilot symbol, which can handle complex information forchannel equalization, with the use of at leas two symbols, bycalculating complex information from demodulation signal pointinformation of at least two sub carriers. In addition, since complexinformation is calculated by use of demodulated signal point informationof an identical sub carrier, it is possible to obtain complexinformation with respect to each sub carrier.

Meanwhile, in this embodiment, a pilot symbol was configured bycontiguous two symbols P1, P2, and there is not necessarily such anecessity that symbols, which configure a pilot symbol, are continuing.In this regard, however, it is desirable that they are continuing incase that an influence of disturbance etc. was taken into consideration.

Sixth Embodiment

A sixth embodiment can improve accuracy of division in fixed pointcalculation, or can reduce a circuit size of a divider, by carrying outquadrant correction from a relation of two demodulated signal points, soas for a scope of inclination a to become −1≦a≦1, on the occasion ofobtaining inclination a of the straight line L1 in the third throughfifth embodiments.

For example, in case that a status of a channel is good, inclination ofthe straight line L0 shown in FIG. 7 and FIG. 1I becomes a value whichis close to infinity, and a bit width for representing that inclinationbecomes very large at the time of calculation, which will inviteincrease of a calculation amount and increase of a circuit size.

Consequently, in this embodiment, quadrant correction is carried out soas for a threshold value of inclination of the straight line L1 showinga channel characteristic to become 1. Here, it is assumed thatcoordinates of two demodulated signal points (the points R_(m) andR_(m+1) in FIG. 7, FIG. 9, and the points R1 and R2 in FIG. 11) are setto (x0, y0), (x1, y1), respectively. Meanwhile, it is assumed that acoordinate in an I axis direction is x, and a coordinate in a Q axisdirection is y.

Firstly, |x1−x0| and |y1−y0| are obtained, respectively. Next,inclination a and segment b of a straight line (the straight line L1 inFIG. 7, FIG. 9, FIG. 11) are obtained by the following formulas (1)through (4).

In case of |y1−y0|≦|x1−x0| (hereinafter, Case 1),a=(y1−y0)/(x1−x0)  (1)b=y1−a.x1 or b=y0−a.x0  (2)

In case of |y1−y0|>|x1−x0| (hereinafter, Case 2),a=(x1−x0)/(y1−y0)  (3)b=x1−a.y1 or b=x0−a.y0  (4)

Therefore, a scope of the inclination a, which is used for calculation,becomes −1≦a≦1. That is, in the case 2, the inclination a and thesegment b become inverse functions of the straight line L1. Next, aphase 0 of a channel characteristic is obtained by the followingformulas (5) through (8).

In case of the case 1 and the segment b>0,θ=tan⁻¹(a)  (5)

in case of the case 1 and the segment b<0,θ=tan⁻¹(a)+π  (6)

In case of the case 2 and the segment b≧0,θ=tan⁻¹(a)+π/2  (7)

in case of the case 2 and the segment b<0,θ=tan⁻¹(a)−π/2  (8)

In addition, an amplitude A of a channel characteristic is obtained bythe following formula (9).A=|b|/(a ²+1)^(1/2)  (9)

In this manner, according to the six embodiment, it is possible toimprove accuracy of division in fixed point calculation, and to reduce acircuit size of a divider, by suppressing inclination of a straightline, which is obtained from two or more demodulated signal pointinformation within a predetermined value.

Seventh Embodiment

FIGS. 12A and 12B are view which schematically shows a part of atransmission frame on a time axis in a seventh embodiment of theinvention. A major configuration of a communication apparatus of thisembodiment is almost the same as that of the first embodiment which wasdescried in FIG. 1.

In the seventh embodiment, a configuration for taking the average ofcomplex information for N symbols, in order to improve accuracy more, inthe first through fifth embodiments, will be described. FIG. 12A shows acase of taking the average of complex information which is obtained fromdemodulated signal points of two symbols, in the example of the fourthembodiment which was described in FIG. 8, and FIG. 12B shows a case oftaking the average of complex information by use of demodulated signalpoint information of 2 symbols, in the example of the second embodimentwhich was described in FIG. 4.

In a transmitting device 10, in case of taking the average of N symbols,contiguous identical data of N−1 symbols are further added to a pilotsymbol. In an example of FIG. 12A, since the average of 2 symbols istaken, contiguous identical data of 2−1=1 symbol (K−1 symbols) is added,in addition to contiguous identical data of 3 symbols in case of nottaking the average. In addition, in an example of FIG. 12B, contiguousidentical data of 2−1=1 symbol is added, in addition of contiguousidentical data of 4 symbols in case of not taking the average.

In a receiving device 20, as shown in FIGS. 12A and 12B, sincecontiguous identical data of 1 symbol is added to a pilot symbol,firstly, demodulation is carried out as to symbols to be demodulatedoriginally, to obtain complex information, and furthermore, demodulationis carried out with shifting an 1 symbol portion to obtain complexinformation. Then, the average of these two complex information is takenby a channel frequency characteristic estimation section, and estimationof a channel characteristic is carried out.

In this manner, according to the seventh embodiment, it is possible toimprove accuracy of complex information, and to improve channelcharacteristic estimation accuracy, since a channel characteristic isestimated from the average of a plurality of complex information.

Eighth Embodiment

FIGS. 13A and 13B are block diagrams which shows a major configurationof a communication apparatus which relates to an eighth embodiment ofthe invention. Particularly, FIG. 13A is a block diagram which shows atransmitting device which configures the communication apparatus, andFIG. 13B is a block diagram which shows a receiving device whichconfigures the communication apparatus. Meanwhile, identical referencenumerals and signs are given to constituent elements which are similarto those in the first embodiment.

A transmitting device 50 in the eighth embodiment is configured byhaving a boundary data output section 51 which outputs boundary data,together with a transmission data output section 11, a pilot data outputsection 12, a switch 13, a symbol mapper 14, an inverse wavelettransform unit 15, a D/A converter 16. Meanwhile, in the transmittingdevice 50, the boundary data output section 51 and the switch 13 have afunction of boundary symbol output means.

In addition, a receiving device 60 is configured by having a boundarysymbol extraction section 61 which extracts a boundary symbol from areceived signal, together with an A/D converter 21, a wavelet transformunit 22, a pilot symbol extraction section 23, a channel frequencycharacteristic estimation section 24, and a channel equalizer 25.Meanwhile, in the receiving device 60, the boundary symbol extractionsection 61 has a function of boundary symbol extraction means.

FIG. 14 is a view which schematically shows a part of a transmissionframe on a time axis in the eighth embodiment. As shown in FIG. 14, inthis embodiment, in case of disposing a pilot symbol in datatransmission by use of the DWMC transmission method, a boundary symbolB, to which a known signal B 1, which is different from a known signalto be given to a pilot symbol, was given, is inserted between a pilotsymbol and a data symbol.

The receiving device 60 extract a boundary symbol from received signalsin the boundary symbol extraction section 61, and the channel equalizer25 estimates a channel characteristic by a pilot symbol, when it detectsa boundary symbol, and starts equalization of a channel.

In case that a synchronization position varies widely by an abruptchange of a channel, there occurs such a case that it is not possible toaccurately get hold of a boundary of a pilot symbol and a data symbol inthe receiving device side. Therefore, in this embodiment, even if asynchronization position varies widely in this manner, it is possible tofit a synchronization position, by use of the boundary symbol.

It becomes possible to make this boundary symbol hold a function whichhas a resemblance to that of a synchronization symbol of a transmissionframe, but it is possible to take synchronization even in a informationsymbol, and therefore, it becomes possible to fit a synchronizationposition without carrying out a re-transmit request, and it is possibleto follow fluctuation of a channel without lowering transmissionefficiency.

In this manner, according to the eighth embodiment, it is possible toaccurately follow abrupt channel fluctuation, since a boundary symbol isdisposed between a pilot symbol and a data symbol, and demodulation ofthe pilot symbol is carried out on the basis of that boundary symbol.

Meanwhile, in the above-described each embodiment, contiguous identicaldata, which configures a pilot symbol, is given to all multi carriers.It is possible to carry out channel equalization processing to all multicarriers, by transmitting a known signal to all carriers.

In addition, as to a pilot symbol in each embodiment and also, aboundary symbol in the eighth embodiment, insertion, non-insertion maybe determined, in accordance with a status of a channel which isdetected in the receiving device. In addition, an insertion distance ofa pilot symbol and/or a boundary symbol may be determined.

Meanwhile, determination processing of selection of insertion,non-insertion, and an insertion distance of a pilot symbol and/or aboundary symbol may be carried out in any one of the transmittingdevice, the receiving device. In case that this determination is carriedout in the transmitting device, it has determination means which carriesout determination processing in accordance with information which showsa status of a channel from the receiving device, and controls the switch13, the pilot data output section 12 and/or the boundary data outputsection 61. In case that this determination is carried out in thereceiving device, determination processing is carried out in the channelfrequency characteristic estimation section 24, or determination meansis further disposed in the receiving device to carry out determinationprocessing. A result, which was determined in the receiving device, isused for processing in the transmitting device.

Meanwhile, as a parameter which shows a status of the above-describedchannel, used are CINR (Carrier power-to-Interference and Noise powerRatio) to be obtained from the channel estimator which carries outestimation of a channel on the basis of a received signal in thereceiving side device, amplitude information to be obtained from achannel equalizer, a bit error rate in the receiving side device, a dataretransmission rate of the transmission signal, and a transmission rateof the transmission signal, a signal power to interference power ratio(SIR), and so on.

This application is based upon and claims the benefit of priority ofJapanese Patent Application No. 2004-121373 filed on Apr. 16, 2004, thecontents of which are incorporated herein by reference in its entirety.

The invention has such an advantage that it becomes possible to use apilot symbol which can handle complex information, in data transmissionof a multi carrier transmission system which depends on wavelettransform based OFDM for carrying out real coefficient wavelettransform, and is useful for a communication apparatus and acommunication method etc. which uses a multi carrier transmission systemfor carrying out data transmission by use of digital modem processingwith the use of a real coefficient wavelet filter bank.

1. A communication apparatus of a multi carrier transmission system,which carries out data transmission by digital modem processing,comprising: a modulator which inserts at least one symbol, to whichcontiguous identical data was given, into a transmission signal as apilot symbol, and carries out digital multi carrier modulationprocessing of transmission signals by use of a filter bank subjectingwavelet transformation; and a transmitter which transmits thetransmission signal including said pilot symbol, which was subjected thedigital multi carrier modulation processing by said modulator.
 2. Thecommunication apparatus as set forth in claim 1, further comprising apilot symbol generator which gives the contiguous identical data, insaid at least one symbol, to generate the pilot symbol.
 3. Thecommunication apparatus as set forth in claim 1, wherein, in case that Npieces of complex information based on the pilot symbol are obtained andits average is used, said pilot symbol is configured by further addingN−1 symbols to which the contiguous identical data was given.
 4. Thecommunication apparatus as set forth in claim 1, wherein, by use ofinformation which shows a channel status regarding each sub carrier,which is obtained on the basis of a received signal in a communicationapparatus of a receiving side, it is determined whether said pilotsymbol is inserted into the transmission signal or not.
 5. Thecommunication apparatus as set forth in claim 4, wherein, as informationwhich shows the channel information, used is at least one of CINR(Carrier power-to-Interference and Noise power Ratio) to be obtainedfrom a channel estimator which carries out estimation of a channel onthe basis of the received signal in the communication apparatus of saidreceiving side, amplitude information to be obtained from a channelequalizer which carries out equalization of a channel on the basis ofthe received signal in the communication apparatus of said receivingside, a bit error rate in the communication apparatus of said receivingside, a data retransmission rate of said transmission signal, and atransmission rate of said transmission signal.
 6. The communicationapparatus as set forth in claim 1, wherein, by use of information whichshows a channel status regarding each sub carrier which is obtained onthe basis of a received signal in a communication apparatus of areceiving side, timing of inserting said pilot symbol into thetransmission signal is determined.
 7. The communication apparatus as setforth in claim 1, wherein, by use of a boundary symbol having contiguousidentical data which is different from the contiguous identical data ofsaid pilot symbol, which is inserted between said pilot symbol and datasymbol in the transmission signal, said transmitter transmits thetransmission signal.
 8. The communication apparatus as set forth inclaim 7, wherein, by use of information which shows a channel statusregarding each sub carrier which is obtained on the basis of a receivedsignal in a communication apparatus of a receiving side, it isdetermined whether said boundary symbol is inserted into thetransmission signal.
 9. The communication apparatus as set forth inclaim 7, wherein, by use of information which shows a channel statusregarding each sub carrier which is obtained on the basis of acommunication apparatus of a received signal in a receiving side, timingof inserting said boundary symbol into the transmission signal isdetermined.
 10. The communication apparatus as set forth in claim 1,wherein said transmitter transmits the transmission signal through apower line.
 11. A communication apparatus of a multi carriertransmission system, which carries out data transmission by digitalmodem processing, comprising: a receiver which receives a transmissionsignal including a pilot symbol configured by at least one symbol towhich contiguous identical data was given; and a demodulator whichcarries out digital multi carrier demodulation processing of thetransmission signal received by said receiver by use of a filter banksubjecting wavelet transformation.
 12. The communication apparatus asset forth in claim 11, further comprising a pilot symbol extractor whichinputs a transmission signal including said pilot symbol and extractsthis pilot symbol.
 13. The communication apparatus as set forth in claim12, further comprising an equalizer which carries out equalization of achannel, in which a channel status is estimated by use of complexinformation which is obtained on the basis of said pilot symbol.
 14. Thecommunication apparatus as set forth in claim 11, wherein, in case thata filter length, which is included in said filter bank subjecting thewavelet transformation, is assumed to be K symbols, said pilot symbol iscomposed of at least contiguous 2K−1 symbols to which the contiguousidentical data was given, and said receiver obtains complex informationby demodulating K-th symbol or later, out of at least 2K−1 symbols towhich said contiguous identical data, which is included in said pilotsymbol, was given.
 15. The communication apparatus as set forth in claim11, wherein, in case that a filter length, which is included in saidfilter bank subjecting wavelet transformation, is assumed to be Ksymbols, said pilot symbol is composed of at least contiguous K symbolsto which the contiguous identical data was given, and said receiverincludes Fourier transformer which obtains complex information byFourier-transforming the contiguous identical data of one symbol out ofK-th symbol or later of said pilot symbol.
 16. The communicationapparatus as set forth in claim 11, wherein said receiver includes acomplex information estimator which estimates complex information on thebasis of said demodulated transmission signal.
 17. The communicationapparatus as set forth in claim 16, wherein said pilot symbol iscomposed of one symbol to which contiguous identical data was given, andsaid complex information estimator estimates said complex information onthe basis of demodulation information of adjacent sub carriers, amongdemodulation information of symbols to which the contiguous identicaldata was given.
 18. The communication apparatus as set forth in claim17, wherein said complex information estimator estimates said complexinformation on the basis of a straight line running through a receivedsignal point which is included in said demodulation signal, andestimates said complex information by use of an inverse function of thatstraight line, in case that a size of inclination of said straight line.19. The communication apparatus as set forth in claim 16, wherein, incase that a filter length, which is included in said filter banksubjecting wavelet transformation, is assumed to be K symbols, saidpilot symbol has contiguous K−1 symbols to which the contiguousidentical data was given, and said complex information estimatorestimates said complex information on the basis of demodulationinformation of adjacent sub carriers, among demodulation information ofK−1 symbols, to which said contiguous identical data was given.
 20. Thecommunication apparatus as set forth in claim 16, wherein said pilotsymbol is composed of a first symbol and a second symbol, to which thecontiguous identical data was given, and said complex informationestimator estimates complex information in said sub carrier, on thebasis of demodulation information of an identical sub carrier in each ofdemodulation information of said first symbol and said second symbol.21. The communication apparatus as set forth in claim 11, wherein, incase that N pieces of said complex information based on the pilot symbolare obtained and its average is used, said pilot symbol is configured byfurther adding N−1 symbols to which the contiguous identical data wasgiven.
 22. The communication apparatus as set forth in claim 1, wherein,by use of information which shows a channel status regarding each subcarrier, which is obtained on the basis of a received signal in acommunication apparatus of a receiving side, it is determined whethersaid pilot symbol is inserted into the transmission signal or not. 23.The communication apparatus as set forth in claim 22, wherein, asinformation which shows said channel information, used is at least oneof CINR (Carrier power-to-Interference and Noise power Ratio) to beobtained from a channel estimator which carries out estimation of achannel on the basis of the received signal in the communicationapparatus of said receiving side, amplitude information to be obtainedfrom a channel equalizer which carries out equalization of a channel onthe basis of the received signal in the communication apparatus of saidreceiving side, a bit error rate in the communication apparatus of saidreceiving side, a data retransmission rate of said transmission signal,and a transmission rate of said transmission signal.
 24. Thecommunication apparatus as set forth in claim 11, wherein, by use ofinformation which shows a channel status regarding each sub carrierwhich is obtained on the basis of a received signal in a communicationapparatus of a receiving side, timing of inserting said pilot symbolinto the transmission signal is determined.
 25. The communicationapparatus as set forth in claim 11, wherein, by use of a boundary symbolhaving contiguous identical data which is different from the contiguousidentical data of said pilot symbol, which is inserted between saidpilot symbol and data symbol in the transmission signal, saidtransmitter transmits the transmission signal.
 26. The communicationapparatus as set forth in claim 25, wherein, by use of information whichshows a channel status regarding each sub carrier which is obtained onthe basis of a received signal in a communication apparatus of areceiving side, it is determined whether said boundary symbol isinserted into the transmission signal.
 27. The communication apparatusas set forth in claim 25, wherein, by use of information which shows achannel status regarding each sub carrier which is obtained on the basisof a communication apparatus of a received signal in a receiving side,timing of inserting said boundary symbol into the transmission signal isdetermined.
 28. The communication apparatus as set forth in claim 11,wherein said receiver receives the transmission signal through a powerline.
 29. A communication method of a multi carrier transmission system,which carries out data transmission by digital modem processing, thecommunication method comprising the steps of: inserting at least onesymbol, to which contiguous identical data was given, into atransmission signal as a pilot symbol; carrying out digital multicarrier modulation processing of the transmission signal by use of afilter bank subjecting wavelet transformation; and transmitting thetransmission signal including said pilot symbol, to which the digitalmulti carrier modulation processing was carried out.
 30. A communicationmethod of a multi carrier transmission system, which carries out datatransmission by digital modem processing, the communication methodcomprising the steps of: receiving a transmission signal including apilot symbol configured by at least one symbol to which contiguousidentical data was given; and carrying out digital multi carrierdemodulation processing of the transmission signal thus received by useof a filter bank subjecting wavelet transformation.